ISCO is a new biannual symposium with its first issue held in Hammamet, Tunisia in March 2010.
The symposium aims to bring together researchers from all the communities related to combinatorial optimization,
including algorithms and complexity, mathematical programming and operations research.
It is intended to be a forum for presenting original research in these areas and especially in their intersections.
Quality papers on all aspects of combinatorial optimization, from mathematical foundations and theory of algorithms
to computational studies and practical applications, are solicited.

Spring school

ISCO 2012 will be preceded by a spring school on "Mathematical Programming and Design of Approximation Algorithms".
David Shmoys and David Williamson will give 16 hours of lectures on April 17-18, 2012.

Abstract: Directed hypergraphs are a natural generalization of digraphs and
are a combinatorial model that turns out to be useful in several application domains
(databases, logic, artificial intelligence etc.). Although in general the computation of shortest hyperpaths
in directed hypergraphs is an NP-hard problem, for suitable cost measures such problem becomes tractable.
In this paper, after discussing the structural properties of hyperpaths (with particular attention to the role
of cycles in hyperpaths and to canonic form of hyperpaths), we present a taxonomy of hyperpath cost functions
and we study the relationships between the classes of cost functions on hyperpaths and the structure of the
corresponding optimal hyperpaths. Finally we illustrate for what classes in the taxonomy shortest hyperpaths
can be computed in polynomial time.

Abstract: We present an approach for structured integer programs that solves well-chosen restrictions
of the problem to produce high-quality solutions quickly. Column generation is used both for automatically
generating the restrictions and for producing bounds on the value of an optimal solution.
We present computational experience for fixed-charge multi-commodity flow and inventory routing problems.

Abstract: I shall discuss recent work (much of it joint with biologists Adi Livnat and Marcus Feldman)
on some central problems in Evolution that was inspired and informed by computational ideas.
Considerations about the performance of genetic algorithms led to a novel theory on the role of sex in
Evolution based on the concept of mixability. And a natural random process on Boolean functions can help us
understand better Waddington’s genetic assimilation phenomenon, in which an acquired trait becomes genetic.

Abstract: Passenger railway systems are highly complex systems requiring the solution of several planning problems
that can be analyzed and solved through the application of mathematical models and optimization techniques,
which generally lead to an improvement in the performance of the system, and also to a reduction in the time
required for solving these problems.
The planning process is generally divided into several phases: Line Planning, Train Timetabling, Train Platforming,
Rolling Stock Circulation and Crew Planning. In this lecture, after a description of the whole planning process and
of its main phases, the Train-Unit Assignment Problem, an important NP-hard problem arising in the Rolling
Stock Circulation phase, is considered in detail.
In the Train-Unit Assignment Problem (TUAV), we are given a set of timetabled trips, each with a required number
of passenger seats, and a set of different train units, each having a cost and consisting of a self-contained train
with an engine and a set of wagons with a given number of available seats. TUAV calls for the minimum cost
assignment of the train units to the trips, possibly combining more than one train unit for a given trip,
so as to fulfil the seat requests.
Two Integer Linear Programming (ILP) formulations of TUAV are presented, and valid inequalities are introduced
for strengthening the corresponding Linear Programming (LP) relaxation. Additional relaxations, based on the
Lagrangian approach and on the solution of a restricted problem associated with a peak period (i.e., with a subset
of simultaneous trips that must be assigned to distinct train units), are considered for the effective computation
of tight lower bounds. Constructive heuristic algorithms, based on the previously considered relaxations, are proposed,
and their solutions are improved by applying local search procedures.
Extensive computational results on real-world instances are reported, showing the effectiveness of the proposed
bounding procedures and heuristic algorithms.

Papers presenting original unpublished results in all areas of combinatorial optimization and its applications are welcome.

Topics of interest include, but are not limited to:

Approximation algorithms

Branch-and-bound algorithms

Branch-and-cut-and-price algorithms

Computational biology

Computational complexity

Computational geometry

Constraint Programming

Cutting plane algorithms

Exact and parameterized algorithms

Graph and network algorithms

Interior point methods

Linear and nonlinear integer programming

Local search algorithms

Metaheuristics

On-line algorithms

Polyhedral combinatorics

Randomized algorithms

Scheduling algorithms

There will be two types of submissions:

a) Regular papers

They should be of at most 12 pages, including front matter and bibliography,
in LNCS style.
Proofs omitted due to space constraints should be included in a clearly marked appendix
which will be taken into account by the program committee members and the reviewers,
but it will not be published in the proceedings.
Simultaneous submissions to other conferences with published proceedings or journals are not allowed.

Accepted regular papers will be published by Springer-Verlag in the Lecture Notes in Computer Science
(LNCS) series in a post-conference proceedings volume.
The authors will have to prepare their camera-ready version two weeks after the end of ISCO 2012.

b) Short papers

They should be of at most 4 pages (including front matter and bibliography) with no optional appendix.
Accepted short papers will be included in a volume of local proceedings.

special issues

The following Special Issues of International Journals will be associated with ISCO 2102:

A special issue of Mathematical Programming Series B on "Combinatorial Optimization".
See here for the CFP for this issue.

A special issue of Theoretical Computer Science on "Combinatorial Optimization: Theory of algorithms and complexity".
See here for the CFP for this issue.

A special issue of RAIRO-Operations Research on "Combinatorial Optimization".
See here for the CFP for this issue.

accepted regular papers

To be published in the LNCS post-conference proceedings volume.
(37 out of 94, acceptance rate 39.4%)

The material for the course will be drawn from our recent book
The Design of Approximation Algorithms (DAA),
and be augmented by several recent papers. We list below the topics of the course,
the associated sections of the book and the related additional papers
(though the papers cited in these book sections might also be covered more completely than in the text).
The list below is probably somewhat too ambitious for the allotted time.

How to reach your hotel from the airport

There are various options to reach the downtown hotels depending on whether you want to use public transportation or taxi.By public transport: The blue metro line goes all the way from the airport to downtown and passes through
the Syndagma metro station (where you can connect with the red line) and the Monastiraki metro station
(where you can connect with the green line that goes towards AUEB). Please do not confuse the metro line with the
suburban railway system, which departs from the adjacent platform and is not convenient for going downtown.
The metro line takes about 35-40 minutes to Syndagma and the ticket from the airport costs 8 euros (note that a
regular metro ticket costs only 1.40 as long as you use it within the city, it is only for the airport that costs 8 euros).
The metro operates from 5:30 am till around midnight. Within the city it runs pretty frequently but the departures to/from the
airport are only every 30 minutes (normally at 5 and 35 past every hour).
Apart from the metro, and especially if you arrive late, you can also take the bus X95 which also goes to Syndagma square.
The bus departs every 15 minutes and the ticket costs 5 euros.By taxi: During the day there is now a standard rate of 35 euros to the city center from the airport.
If you arrive past midnight, the tariff is 50 euros.

How to come to the conference venue

The conference will take place in the main building of AUEB (the Athens University of Economics and Business).
AUEB is located in the city center, and the main building is on 76 Patission st. If your hotel is not within walking
distance, the best way to come to AUEB is by using the green line and getting off at Victoria station. It is then a 5 minute walk
till the main building. There are also several buses and trolleys that stop just outside AUEB such as the buses
608, 622, A8, B8, Γ8 and the trolleys 3, 5, 11, 13, 14. In the map below you can have a better view of where the main
building of AUEB is located.

How to reach the Acropolis Museum for the social event

To come to the social event on Friday evening, one option is to take the metro from Victoria station near AUEB
and switch in Omonoia to the red line. Then you get off at the Akropolis station and the museum is just a few minutes walk from
there. Alternatively you can take the trolley 5 (just across from the main building) and get off at the Makrygianni stop.

accommodation

The Athens University of Economics and Business (AUEB), where the conference will take place,
is located in the centre of Athens where many hotels can be found.
We include here some recommended hotels, in walking distance from AUEB, and their offers for ISCO 2012.